Top Gun Phlebotomy – Butterfly Use: The Good, the Bad, and the Ugly

Expires: February 17, 2026


Photo of Brad Karon, M.D., Ph.D.

Brad Karon, M.D., Ph.D.

Chair, Division of Clinical Core Laboratory Services
Professor of Laboratory Medicine and Pathology
Mayo Clinic, Rochester, Minnesota


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Transcript and References


Dr. Pritt: Hi, I’m Bobbi Pritt, Director of the Clinical Parasitology Lab and Vice Chair of Education in the Department of Laboratory Medicine and Pathology at Mayo Clinic. In this month’s “Hot Topic,” my colleague Dr. Brad Karon will discuss recent information on the advantages and disadvantages to using butterfly needles for blood collection. I hope you enjoy this month’s Hot Topic, and I want to personally thank you for allowing Mayo Clinic the opportunity to be a partner in your patient’s health care.

Dr. Karon: For those of you who have not attended our phlebotomy conference here in Rochester, the title of my Hot Topic video today, Phlebotomy Top Gun, may seem a little odd—but I hope I’ll be able to explain to you what is “phlebotomy top gun,” and what we try to do at our annual phlebotomy conference. Today’s Hot Topic video presentation will address the use of butterfly needles for blood collection.


I have no disclosures relevant to today’s presentation.

Which of the following are currently demonstrated to be true regarding butterfly usage?

Every year at the Mayo Clinic Laboratories phlebotomy conference, I present a talk that’s called “Phlebotomy Top Gun.” The format of “Phlebotomy Top Gun” is a case-based presentation. I solicit from you, the attendees, cases, issues, or questions that you like to hear about. I present these as case-based scenarios, and using an audience response voting mechanism, the attendees of the conference vote on the action or answer they feel is appropriate to the case. I then present the collective experience from our practice, and the evidence and data that I can find related to the topic. At the end of the case, the attendees vote again. For each case, I can see whether I’ve been able to change anyone’s mind on the question at issue by presenting the data and information relevant to the particular topic. This is an actual case from a “Phlebotomy Top Gun” presentation at last year’s phlebotomy conference in Rochester. In this case the question was: “Which of the following are currently demonstrated to be true regarding butterfly usage?

  • Answer A: Butterfly usage increases hemolysis rates.
  • Answer B: Butterfly needles cost more than vacutainer needles.
  • Answer C: Use of butterfly needles increases rates of percutaneous needle exposures.
  • Answer D: All of the above are true.

And at this point during the live conference, attendees using an audience response system would vote for the answer they thought was most appropriate or correct, and we get to see in real time the distribution of results from our audience.

Butterfly Usage

There have been a number of published studies examining the effect of use of a butterfly needle, especially a smaller gauge butterfly needle like a 23 or 25-gauge needle, on rates of hemolysis in blood samples. This slide demonstrates the results of one such study performed by Dr. Lippi and colleagues in 2006. In this study, adult volunteers had three separate blood draws using three different types of butterfly needles. Experienced phlebotomy staff did all the blood draws using a vacutainer adapter, so you might say optimal conditions for blood collection using a butterfly needle. 14 different chemical analytes were tested from the tubes collected using either 21-gauge, 23-gauge, or 25-gauge butterfly needles. On average, the results of the biochemical tests did not differ by collection devices. However, potassium and AST—the chemical analytes most sensitive to the effects of hemolysis (both increasing with more free hemoglobin present in the serum or plasma sample)—, showed much more variability in the 23 and 25-gauge device compared to the 21-gauge. In fact, variability in potassium results was two-fold greater when a 25-gauge butterfly was used to draw blood compared to a 21- gauge butterfly. This is one of many studies demonstrating that hemolysis—or the amount of free hemoglobin present in serum or plasma samples—is much more variable when small diameter butterfly needles are used for blood collection. These authors therefore recommended that 25-gauge butterfly needles be used only for newborns or patients with very small veins to avoid rejection of blood specimens for excess hemolysis.

New Butterfly Techniques

The study by Lippi and colleagues that I just highlighted is one of many studies that have historically been used to justify limited use of butterfly needles for blood collection, and very restricted use of smaller gauge 23 and 25-gauge butterfly needles. More recently, at least one manufacturer of butterfly needles has reconfigured their devices to address this issue. In the end, hemolysis induced by collection from small butterfly needles is due to the small diameter inside the needle that blood must travel thru to reach the syringe or vacutainer adapter. By manufacturing the device where the wall of the needle is smaller, one manufacturer has produced a device that has the outside diameter of a 25-gauge butterfly, while maintaining the bore size (or internal diameter) of a 23- gauge needle. Both data from this manufacturer and internal data collected at Mayo Clinic suggests that this device maintains the tube fill rates and levels of free hemoglobin (or hemolysis) that are typically observed for a 23-gauge butterfly device. This device also was reconfigured with additional beveling to decrease pain associated with venipuncture. In recognition of the fact that some advances in manufacturing have allowed the production of small-gauge butterfly needles that may not increase hemolysis rates, guidelines from the Clinical and Laboratory Standards Institute have now been changed to reflect that, “the use of some 25-gauge needles increases the risk of hemolysis and rejected specimens.” Previously, these guidelines suggested that use of any 25-gauge needle would increase the risk of hemolysis.

Butterfly Usage

Among the most commonly cited concerns about butterfly needle usage is that percutaneous needle exposures, and the risk of infectious disease transmission associated with accidental needle sticks in healthcare workers, could be increased with the use of butterfly devices. This study from Yale University examined needlestick exposures over a two-year period from 1993-94. Three-quarters of accidental exposures were due to the use of a hollow-bore device. Among these, luer lock syringes were most common, followed second by butterfly needles, and third, by vacutainer needles. Looking at the rate of percutaneous exposures, the rate of exposure was four times greater with a butterfly needle compared to vacutainer needle blood collection. This study is one of many that demonstrated that use of butterfly collection needles does in fact increase the risk of occupational exposure associated with percutaneous injuries.

One reason—and likely the primary reason—that butterfly needles did result in more percutaneous injuries was the mechanism of safety device activation. In the past, butterfly needles required a two-handed safety device activation, such as pulling down a sleeve or sheath to cover the needle after blood collection. This required removing the needle from the arm and activating the safety device prior to disposal of the needle. This study describes a performance improvement initiative to reduce percutaneous exposures at one hospital. Prior to the intervention, rates of percutaneous exposure were three-fold greater when butterfly needles were used to collect blood specimen compared to vacutainer collections. The intervention in this study was to implement a push-button retractable butterfly needle, eliminating the need for two-handed activation of the safely device, and allowing for safety device activation prior to withdrawal of the needle from the patient’s arm. Over time, the exposure rate associated with the newer butterfly device came down to lower than the rate originally observed for vacutainers. These authors concluded that use of the newer butterfly with one-hand push-button safety activation was as safe as use of a vacutainer needle for blood collection.

Not all sites want to use a push button retractable butterfly needle device, so this study demonstrates results of a similar quality improvement/safely project within a hospital where the intervention in this case was the implementation of a butterfly needle with a safety sheath, which did require a two-hand activation of the safety device. While implementation of a butterfly needle with a safety sheath did reduce percutaneous exposures, rates remained much higher than exposure rates associated with vacutainer needles, and staff continued to have exposures due to incorrect activation of the safety device, or staff simply choosing not to use the safety sheath or device. This study and others like it demonstrate that to make butterfly use safe (or at least as safe as vacutainer needle use) for staff collecting blood, butterfly needles with a push-button retractable safety device should be used, and staff should be trained to never withdraw needles from patients without activating the safety device first.

Because butterfly needles do cost substantially more than vacutainer needles, one question that labs often ponder is why so many nursing staff choose to use butterfly needles for blood collection. This qualitative study asked nursing staff and clinical assistants exactly that question. Interviews were conducted with 11 nurses and 14 clinical assistants trained for blood collection, and themes were described from the transcribed interviews. Four themes emerged: Nurses and clinical assistants liked the mechanical features of the butterfly.  They found it easier to manipulate a butterfly needle compared to a vacutainer. They felt that butterfly collection was appropriate for sicker patients, or patients with poorer veins. And they used butterfly needles when they perceived that patients had or might have poor veins. These results are probably not all that surprising to many people listening today who are responsible for overseeing blood collection, but they do lend some evidence to commonly perceived or accepted reasons why people choose to use butterfly needles.

Summary of Butterfly Usage

Because I can’t go over all of the data and evidence I would normally present in a case at the phlebotomy conference, and that I in fact presented last year, on this slide, I have attempted to summarize the material I presented during this case on butterfly usage last year. Many of the reasons that we have cited for avoiding butterfly blood collection in the past may no longer apply to butterfly needles due to improved design of some devices. In particular, use of a 25-gauge butterfly needle with a wider bore, and use of push-button safety device activation, have reduced concerns related to excess hemolysis and percutaneous exposure of health care workers. While I did not have time to cover this material today, we have noted within our practice here at Mayo Clinic that use of butterfly needles for blood collections can still lead to hemolyzed or clotted blood specimens. And this is particularly true when there are many blood tubes that need to be collected, or very large orders for blood collection. Thus use of smaller gauge butterflies is best limited to pediatric patients or patients with small veins. Institutions should do everything possible to encourage or limit usage of butterfly collection devices to only those with one-hand push-button activation safety device. Strategies that have been effective to limit butterfly usage include training staff first with a vacutainer device before they are allowed to try or get comfortable with a butterfly. Education of staff on cost and potential downsides of butterfly collection (particularly use of butterflies when multiple blood tubes must be collected), and the associated risks—at least in our experience—creates risk of hemolysis and clotting when collecting multiple tubes with a butterfly. And if all else fails, simply limiting access of butterfly devices to pediatric areas or areas where their use is likely to be required.

Which of the following are currently demonstrated to be true regarding butterfly usage…

At this point during the phlebotomy conference, I would then return to the original question that I polled the audience on. The attendees of the conference would use the audience response system to vote again, and I would share with the audience what I believe is the correct or intended response to the case or question. Based upon the available data and our collective experience here at Mayo, my opinion is the single best answer to this question would be option B. It will always be true that butterfly needles cost more than vacutainer needles, or at least until someone makes a much cheaper or less expensive butterfly. While we have identified specific situations (such as large blood collections or the need to collect multiple tubes) where butterfly needles in our experience may increase the risk of hemolyzed or clotted samples, more recent evidence suggests that this is not universally true, or true in all situations. Use of butterfly devices with one-hand push-button safety device activation does not appear to increase the risk of percutaneous exposure for health care workers compared to use of vacutainer needles. So again, in my opinion, the answer to this case is option B

Thank You

Thank you for your time and attendance today. If you liked today’s presentation, or even if you didn’t, please do consider attending our next Phlebotomy conference on April 23rd and 24th, 2020, here in Rochester, MN. Learning takes place via both large-group didactic sessions, and small breakout sessions that allow more interaction with conference speakers. Tours of Mayo Clinic facilities are also offered during the conference. Thank you for listening today, and have a wonderful day.

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This post was developed by our Education and Technical Publications Team.